Active caspase‐3 expression during postnatal development of rat cerebellum is not systematically or consistently associated with apoptosis

Abstract

Development is a dynamic process that includes an intricate balance between an increase in cell mass and an elimination of excess or defective cells. Although caspases have been intimately linked to apoptotic events, there are a few reports suggesting that these cysteine proteases can influence the differentiation and proliferation of cells. Specifically, the active form of caspase-3, which has been classified as an executor of apoptosis, recently has been implicated in a nonapoptotic role in the regulation of the cell cycle, cell proliferation, and cell differentiation. This study investigated the nonapoptotic function and phenotypic expression of active caspase-3-positive cells in the external granule cell layer (EGL) of the postnatal rat cerebellum by using biochemical and immunohistochemical analyses, respectively. Evidence that negates an apoptotic function for the caspase-3-positive EGL cells includes a failure to exhibit chromatin condensation (assessed with TOPRO), phosphatidyl serine externalization (Annexin V labeling), or DNA fragmentation (TUNEL labeling). Proliferative (Ki67-positive) and differentiated (TUJ1-positive) cells within the EGL exhibited a cytosolic expression of caspase-3, whereas terminally differentiated granule cells (NeuN-positive) in the internal granular layer and the migrating granule cells did not express active caspase-3. Thus, this study supports a nonapoptotic role for active caspase-3 in cells residing in the EGL and suggests a possible involvement in EGL proliferation and differentiation.

Loss of Neurons from Laminas I-III of the Spinal Dorsal Horn Is Not Required for Development of Tactile Allodynia in the Spared Nerve Injury Model of Neuropathic Pain

“…Although it has been suggested that the presence of cleaved caspase-3 represents a point of no return in the apoptotic pathway (Huppertz et al, 1999), this form of the enzyme has also been identified in cells that are not undergoing apoptosis (Oomman et al, 2004). We found that astrocytes throughout the spinal cord of both SNI and naive rats showed moderate to high levels of cleaved caspase-3, and a similar observation has been made in naive rat spinal cord in two previous studies (Martin and Liu, 2002;Hoang et al, 2003).…”

Caspase‐3 activation in astrocytes following postnatal excitotoxic damage correlates with cytoskeletal remodeling but not with cell death or proliferation

“…Although the preponderance of data has emerged from work in the immune system and peripheral organs, several studies have also suggested non-apoptotic roles of caspase-3 in the CNS. Under physiological conditions, caspase-3 has been implicated in neuronal cytoskeletal changes (Rohn et al, 2004), in synaptic remodeling (Dash et al, 2000;Shimohama et al, 2001), in neuronal survival associated with preconditioning (Garnier et al 2003;McLaughlin et al, 2003;Tanaka et al, 2004), in the differentiation of cerebellar Bergmann glial cells (Oomman et al, 2004(Oomman et al, , 2005(Oomman et al, , 2006, and as a marker of astroglial subpopulations (Noyan-Ashraf et al, 2005). Accordingly, following excitotoxic damage in the neonatal brain we have demonstrated that presence of cleaved caspase-3 in nitrated reactive astrocytes in the absence of cell death (Acarin et al, 2005).…”

“…In addition, caspase-3 activation and substrate cleavage has been reported in the absence of cell death in gerbil hypoxia (Garnier et al, 2004) and in ischemic tolerance where neuronal caspase-3 is essential for the neuroprotective effect of preconditioning (Garnier et al 2003;McLaughlin et al, 2003;Tanaka et al, 2004). Furthermore, other studies have also demonstrated a role of caspase-3 in the maturation of cerebellar granular cells during development (Oomman et al, 2004) and the differentiation of neural progenitor cells in the olfactory bulb (Fernando et al, 2005;Yan et al, 2001). Progenitor cells that divide and migrate through the rostral migratory stream en route to the olfactory bulb, show cleaved caspase-3 but no signs of cell death (Yan et al, 2001).…”

“…With regards to glial cell differentiation, Oomann and coworkers, who have described cleaved caspase-3 in Bergmann glia during postnatal development in the absence of apoptotic or proliferation markers, have demonstrated a role of this protease in differentiation processes (Oomman et al, 2004(Oomman et al, , 2005(Oomman et al, , 2006. In addition, it was recently shown that constitutive non-apoptotic expression of the cleaved form of caspase-3 occurs in the nuclei of a subpopulation of astrocytes in the cerebellar cortex, hippocampus, and spinal cord of adult rats of different strains, which show expression of the sodium dependent glutamate transporter (EAAT1, GLAST) (Noyan-Ashraf et al, 2005).…”

Neural-Specific Inactivation of ShcA Results in Increased Embryonic Neural Progenitor Apoptosis and Microencephaly

“…In the developing mouse forebrain, the expression pattern of CC3 correlates well with terminal deoxynucleotidyl transferase-mediated biotinylated UTP nick end labeling (TUNEL)-positive cells with the majority of CC3 ϩ cells being TUNEL ϩ (Urase et al, 2003). However, there are reports that CC3 staining does not always correlate with apoptosis; yet, in these special cases, the CC3 ϩ cells do not have any other characteristics consistent with apoptosis such as chromosome condensation, DNA fragmentation, or TUNEL staining (Yan et al, 2001;Lossi et al, 2004;Oomman et al, 2004).…”